Light reflectors for producting a conical divergent light beam



Nov. 21, 1967 M. 1.. FREEMAN 3,354,304 LIGHT REFLECTORS FOR PRODUCING A CONICAL DIVERGENT LIGHT BEAM Original Filed July 1, 1963 d f d 1 1 11 11/ I I I1 111111, I III] and United States Patent ABSTRACT OF THE DISCLOSURE The device relates generally to a reflector for radiant energy and particularly relates to a reflector of light or Other radiant energy for directing the light emitted by a source in a desired direction with a minimum of loss and improved etficiency. Said reflector system comprising an ellipsoidal rear reflector having a light source at the rear focal point and a plurality of annular, spherical, recoupling mirrors disposed in front of said ellipsoidal reflector in order to direct radiation onto said ellipsoidal reflector.

This application is a continuation of my prior, copending application, Ser. No. 292,034, filed on July 1, 1963, entitled Light Reflectors, now Patent No. 3,283,- 142.

Light reflectors are well known which serve the purpose of controlling and directing light emitted by a light source into a desired direction such, for example, as a parallel beam of light or a conical beam of light. To this end, a rear reflector is conventionally provided which collects at least half of the light emitted by the source and directs it, for example, into a parallel beam. Such a reflector is usually further improved by the provision of a front lens which collects another portion of this light emitted by the source to direct it, for example, into a parallel beam.

However, it will be apparent that a large fraction of the light which is not reflected by the rear reflector nor collooted by the front lens is lost. This loss shows up either as heat or else it may produce side light which is undesired and may cause glare.

"In order to improve the efliciency of a light reflector and to reduce glare caused by light emitted in an undesired direction, it has been proposed to provide an additional small front reflector which closely surrounds the light source and is disposed withinthe rear reflector. The front reflector reflects all light which might otherwise emerge in a conical beam onto the rear reflector. However, it will be apparent that this conventional front reflector casts a central shadow thereby removing the middle portion 'of the controlled light beam. Thus, this conventional light reflector system gives very good control of the emerging light but has low efliciency because still a large fraction of the light is lost which is converted into undesirable heat.

Another prior art light reflector utilizes a parabolic rear reflector coupled with a spherical front reflector disposed entirely outside the rear reflector. The parabolic rear reflector will reflect the light from the source into a parallel beam. The spherical front reflector reflects a portion of the light which would otherwise emerge into a conical beam onto the rear reflector. However, unless the spherical front reflector is made very large and bulky, there'will still be a portion of the light which emerges as an undesired conical beam causing glare and distraction. Such a prior art reflector system is relatively large and bulky and still does not eliminate all of the light which emerges in a conical beam.

3,3543% Patented Nov. 21, 1967 It is accordingly an object of the present invention to provide an improved reflector system for directing radiant energy in a desired direction which is relatively small in size and which directs substantially all of the radiant energy into the desired direction thus greatly improving the eflicency.

A further object of the present invention is to provide a reflector system of the type referred to which permits to direct radiant energy into a divergent cone and which minimizes loss of radiant energy which would otherwise result in undesired heat.

Still another object of the present invention is to provide a light reflecting system for radiant energy such, for example, as visible light, infrared light or ultraviolet light which permits an improved control over the direction and distribution of the light with a resulting reduction in the production of heat, an increased efliciency and a savings in the cost of operation.

In accordance with the present invention there is provided a reflector system for directing radiant energy from a source in a desired forward direction. Thus, the reflector system may direct visible light, infrared light or ultraviolet light or other electromagnetic waves or radiant energy. There is provided a source for emitting radiant energy substantially in all directions. This could, for example, be an incandescent or filamentary light or a gasfilled lamp which may be a point source. There is further provided a rear reflector partly surrounding the source in a rearward direction for reflecting a first portion of the radiant energy emitted by the source and for directing the first portion into the desired direction.

For example, it may be desired to direct the radiant energy such as light into a conical divergent beam. A second portion of the radiant energy emitted by the source will, of course, directly emerge in the desired direction. There is finally provided a front reflector disposed ahead of and about the source for reflecting substantially all of the remaining radiant energy emitted by the source toward the rear reflector and then into the desired direction.

Preferably, the reflector system has rotational symmetry utilizing a point source in which case the front reflector may be disposed in a cylinder extending through the edges of the rear reflector. The front reflector includes a plurality of separate portions each reflecting a solid angle of radiant energy from the source onto the rear reflector. As a result, substantially all of the radiant energy is directed into the desired direction.

If the reflector system is designed to direct a conical divergent beam, the front reflector may be of generally cylindrical shape substantially coextensive with the outer edge of the rear reflector. The front reflector may have a plurality of individual portions spaced from each other, each reflecting radiant energy from the source onto the rear reflector and thence into a conical beam.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following descripiton when read in connection with the accompanying drawings, in which the single figure is a sectional view of a floodlight in accordance with the present invention for developing a divergent conical light beam.

Referring now to the figure there is illustrated a reflector system embodying the present invention. The reflector of the drawing is suitable as a floodlight which develops a diverging conical light beam. The reflector has a light source 10, a rear reflector and a front reflector 81. The light source 10 may be any source of visible, infrared, or ultraviolet light, for emitting radiant energy. The light source 10 may, for example be a filamentary 3 source to provide substantially a point source. Altern tively, the light source may be a gas-filled lamp such as a lamp operating with xenon gas, mercury vapor or sodium vapor. The rear reflector 80 has such a shape as to reflect light from the source 10 into a conical beam as indicated by the lines 82. The rear reflector may, for example, consist of metal having a polished inner surface for reflecting the light from the source 10 forwardly. Alternatively, the rear reflector may, for example, be made of glass or some other material provided with a reflecting metallic surface.

The front reflector 81 surrounds the light source 10 in a forward direction and includes three reflecting surfaces 83 which are portions of a sphere. The reflecting surface may be applied to the front surface in any suitable manner. It may be a polished surface layer or the metal of the reflector itself may be polished. The front reflector 81 may be constructed of glass, metal or plastic material. The reflecting surfaces of the front reflector may be blown, cast, embossed, molded, stamped, spun, machined or otherwise shaped. The entire light source may be enclosed in a glass bulb 84 including a transparent front window 85. The front reflector 81 is closed by an opaque reflecting shield 86 having a central aperture 87. The front reflector 81 serves the function to redirect that portion of the radiant energy which is not directly reflected by the rear reflector 80 and which is not directly emitted into a conical forward beam.

Thus, it will be seen that the light is focused through the central aperture 87 and then passes through the front window 85. The reflector 86 may form a portion of a sphere and reflects light onto the rear reflector 80. The front reflector 81 and 86 collect a major portion of the light otherwise lost and directs it toward the rear reflector 80 and then through the aperture 87. As a result, as seen from the source 10, looking toward the front reflector 81, the front reflector appears as the inside surface of a hemisphere. Since the beam is focused in the aperture 87 and since the beamat this point tends to be very hot, it is preferred that no material be disposed in the aperture 87.

It will be understood that the flood beam developed by the reflector may have the shape of its beam and. its focal point changed in any conventional manner, for example, by movable or adjustable lenses.

The principles of the reflector system of the present invention may be applied to many different applications. For example, the reflector system may be utilized as spotlights, automobile headlights, aircraft landing lights,

airport runway lights, signal lights, beacon lights, flash or photoflash units, picture projectors, or for illuminating roadways, for theatrical lighting or lighting in television studios. It may be used for display purposes, as fog lights, airborne flares for ground illumination, photoelectric beams, searchlights, floodlights, for indoor illumination, general lighting or marine lighting.

There has thus been disclosed a reflector system for radiant energy such as infrared, visible or ultraviolet light. The reflector system of the invention is characterized by a greaterefliciency resulting from a smaller loss of light and less generation of heat..The reflector system is so constructed that substantially all the light generated by a light source is converted into a useful beam which may be parallel or conical. The reflector system essentially comprises a rear reflector and a front reflector. The front reflector is so constructed that it presents to the light source a substantially spherical reflecting surface. The light reflected first by the front reflector and then by the rear reflector in turn passes through the front reflector substantially without loss of light.

The invention and its attendant advantages will be understood from the foregoing description. It will be apparent that various changes may be made in the form, construction and arrangement of the parts of. the invention without departing from the spirit and scope. thereof or sacrificing its material advantages, the arrangement hereinbefore described being merely by way of example. I do not wish to be restricted to the specific form shown or uses mentioned except as defined in the accompanying claims, wherein various portions have been separated for clarity of reading and not for emphasis.

I claim:

1. A reflector system for directing radiant energy emitted by a source into a high intensity conical divergent beam in a forward direction, said system comprising:

(a) a source for emitting radiant energy substantially in all directions;

(b) a rear reflector partially surrounding said source for directly reflecting a first portion of the radiant energy of said source into a conical divergent beam in the forward direction and focused in a focal point; and

(c) a front reflector of generally cylindrical shape surrounding said source and said rear reflector, said front reflector having a plurality of individual reflecting surfaces spaced from each other, each providing means to reflect radiant energy from said source onto said rear reflector from which it is formed into said conical beam and focused with the major portion of the radiant energy emitted by said source into said focal point.

2. A reflector system as defined in claim 1, wherein said source is of substantially point shape, wherein said individual reflecting surfaces of said front reflector are interconnected by members disposed along radial lines passing through said source, and wherein said front and rear reflectors are so arranged that said focal point is located beyond a plane passing through the outer edges of said front reflector.

3. A reflector system as defined in claim 1, wherein an additional reflector is provided, said additional reflector having a central aperture disposed at said focal point of said conical beam, said additional reflector being disposed ahead of said front reflector and providing means to reflect radiant energy onto said rear reflector and from which it travels through said aperture.

4. A reflector system as defined in claim 3, wherein said additional reflector forms a portion of a sphere to reflect light onto said rear reflector.

5. A reflector system as defined in claim 3, wherein an envelope is provided enclosing said source, rear reflector,

front reflector and additional reflector, a transparent window forming part of said envelope and disposed in the path of said conical beam, said window being spaced from said additionalreflector a distance suflicient so that said beam heats said front window to a temperature below that at which said window will soften.

6. A reflector system as defined in claim 1, wherein an envelope is provided for enclosing said source, said front reflector and said rear reflector comprising a portion of said envelope.

References Cited UNITED STATES PATENTS 657,693 9/1900 Egnell 2404l.35 1,095,583 5/1914 Luyties 24041.35 1,641,714 9/1927 Whalen 240-41. 36 1,723,535 8/1929 Whalen 2404l.36 2,004,183 6/1935 Benjamin 2404l.35 X

NORTON ANSHER, Primary Examiner. QGAN, W M, FRYE, Assistant Examiners. 

1. A REFLECTOR SYSTEM FOR DIRECTING RADIANT ENERGY EMITTED BY A SOURCE INTO A HIGH INTENSITY CONICAL DIVERGENT BEAM IN A FORWARD DIRECTION, SAID SYSTEM COMPRISING: (A) A SOURCE FOR EMITTING RADIANT ENERGY SUBSTANTIALLY IN ALL DIRECTIONS; (B) A REAR REFLECTOR PARTIALLY SURROUNDING SAID SOURCE FOR DIRECTLY REFLECTING A FIRST PORTION OF THE RADIANT ENERGY OF SAID SOURCE INTO A CONICAL DIVERGENT BEAM IN THE FORWARD DIRECTION AND FOCUSED IN A FOCAL POINT; AND (C) A FRONT REFLECTOR OF GENERALLY CYLINDRICAL SHAPE SURROUNDING SAID SOURCE AND SAID REAR REFLECTOR, SAID FRONT REFLECTOR HAVING A PLURALITY OF INDIVIDUAL REFLECTING SURFACES SPACED FROM EACH OTHER, EACH PROVIDING MEANS TO REFLECT RADIANT ENERGY FROM SAID SOURCE ONTO SAID REAR REFLECTOR FROM WHICH IT IS FORMED INTO SAID CONICAL BEAM AND FOCUSED WITH THE MAJOR PORTION OF THE RADIANT ENERGY EMITTED BY SAID SOURCE INTO SAID FOCAL POINT. 